Subduction Zone Effect on the Structure of the Small-Scale Currents at Core-Mantle Boundary

TL;DR

This study investigates how subduction zones influence small-scale current vortices near the core-mantle boundary, revealing a correlation with seismic wave velocity anomalies and suggesting core-mantle interactions affect core liquid circulation.

Contribution

It provides the first comparison of vortex kinematics with seismic anomalies near subduction zones, highlighting their complex relationship and potential impact on core-mantle dynamics.

Findings

Vortex trajectories align with seismic velocity anomalies near subduction zones.

Subduction-related mantle heterogeneities influence small-scale core boundary currents.

Oceanic crust subduction may penetrate into the liquid core, affecting core circulation.

Abstract

The purpose of this work is to compare kinematics of small-scale current vortices located near the core-mantle boundary with high-speed anomalies of seismic wave velocity in the lowest mantle asso-ciated with the subduction zones. The small-scale vortex paths were early obtained by the authors in the frame of the macro model of the main geomagnetic field sources. Two sources were chosen whose kine-matics are characterized by the complete absence of the western drift and whose paths have a very com-plex shape. Both sources are located in the vicinity of the subduction zones characterized by the extensive coherent regions with increased speed of seismic waves in the lowest mantle. One of them is geographically located near the western coast of Canada and the second one is located in the vicinity of Sumatra. For this study we used the global models of the heterogeneities of seismic wave velocity. It was obtained that the complex trajectories of the vortices is fully consistent with the high-speed anomalies of seismic wave velocity in the lowest mantle. It can be assumed that mixing up with the matter of the lowest mantle, the substance of the liquid core rises along the lowest mantle channel and promotes its further increase. In addition, the volume of oceanic crust, subducted millions of years ago, turned out to be sufficient to penetrate into the liquid core, forming the complex shape restrictions for free circulation of the core liquid.